User manual

H70.0.21.6C-01 Operating Manual GMH 3511 page 9 of 14
6.4 Calibration of pH measurement
The electrode data of pH electrodes are subject to fluctuation due to ageing and manufacturing tolerances.
Therefore it is necessary to check the calibration with buffer solutions before measurements take place. If
deviations are too large, a recalibration is necessary.
Buffer solutions are liquids with an accurate pH-value. The standard series GPH (buffer capsules to be
mixed with water pH 4.01, pH 7.00 and pH 10.01) can be used for calibration
Service life of a buffer solution is limited and will be further reduced unless the electrodes are
properly rinsed and dried when changing over the solutions. This may even result in incorrect
calibration! We recommend to use new buffer solution for calibration, as far as possible, and to
rinse with deionized or distilled water.
6.4.1 How to prepare calibration buffers of standard GPH series (capsules)
See notes B.
6.4.2 Automatic temperature compensation during calibration
Both the signal of the pH-electrode and the pH-buffer are depending on temperature. If a temperature probe
is connected, the temperature influence of the electrode is compensated automatically during measuring as
well as during calibration. Otherwise enter actual buffer temperature as accurate as possible (see below).
6.4.3 How to carry out calibration
Please note: the calibration can only carried out at a temperature range of 0 - 60°C !
If you have not yet done so set device to measuring mode ’pH’.
Carefully remove electrode safety cap (Attention! Contains 3 mol KCl!).
Rinse electrode with distilled water and dry it carefully.
How to start calibration: press key for 2 seconds.
The display will prompt you to measure the first calibration solution.
You can abort calibration at any time by pressing key. In such a case the last calibration before this one
remains valid.
1. Calibration point 1: ‘Pt. 1’
*1)
Place electrode and temperature probe
(if any) in the neutral solution stirring
gently.
(For 1-point calibration: solutions with
arbitrary pH value (e.g. pH 4) can be uses)
As soon as the measured pH value got
stable the next calibration step will be
displayed.
No
temperature sensor:
manual input of
temperature of buffer 1
Use or to enter the temperature of
the buffer solution.
Use
to confirm the value; the next
calibration step is displayed.
2. Rinse electrode in distilled or deionized water, dry electrode
3. Calibration point 2: ‘Pt. 2’
*1)
Place electrode and temperature probe
(if any) in the second buffer solution (e.g.
for standard series this is: pH 4.0 or pH
10.0) and stir gently.
As soon as the measured pH value got
stable the next calibration step will be
displayed.
No
temperature sensor:
manual input of
temperature of buffer 2
Use or to enter the temperature of
the buffer solution.
Use
to confirm the value; the next
calibration step is displayed.
Calibration has finished, the display shows the electrode’s state rating.
4. Rinse electrode in distilled or deionized water, dry electrode
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